By type r head do you mean an ITR head (b18 C8 etc) or a EK9 type r head (B16b) i dont think it will give you any power increase, coz is just the same only its got double valve springs (allowing a 8700rpm limiter on ITR) and there meant to be hand finished on the ports too, although when you look at the set side by side you cant really tell the differance.
I think anyways some1 correct me if i'm wrong..........

So as there the same anyway you wont have to change the pistons, however ITR or EK9 pistons will give you more compression equaling more power.